Material for and process of pickling and cleaning



March 26, 1935. A. E. CHESTER Q 1,995,766

MATERIAL FOR AND PROCESS OF PICKLING AND CLEANING Filed June 1, 1934 TiuzlnrL l0 /0 INVENTOR ATTORN E Y5 Patented Mar. 26, 1935 UNITED STATES.

MATERIAL FOR AND PROCESS OF PICKLING AND CLEANING Allan E. Chester, Cleveland, Ohio, assignor to Fen-o Enamel Corporation, Cleveland, Ohio, a.

corporation of Ohio Application June 1, 1934, Serial No. 728,548

27 Claims.

This application is a continuation in part of my co-pending application, Serial No. 694,028, filed October 18, 1933 for Cleaning and pickling process composition and apparatus.

The present invention relates to the cleaning and pickling of iron and steel generally, including, for example, high carbon steel, low carbon steel, such, for example, as enamellers steel, alloy steel and iron, wrought iron, cast iron, cast steel, malleable iron, semi-steel, and drop forgings of various compositions.

An object of the invention is to provide an improved pickling bath which accomplishes the pickling operation in less time than is required by the baths now commonly in use.

Another object of the invention is to provide an electric pickling system that is neither im practical nor too costly to be used by steel manufacturers and fabricatorsthe'system being one capable of handling large quantities of work, for

example, quantities as large as are at present cleansed in non-electric pickling systems that have been eitherimpractical or too costly for the pickling of large quantities of work commercially. Another object of the invention is the provision of' an electric pickling system in which the above-mentioned improved pickling bath is used as an electrolyte, the present process providing an electrolyte of greater chemical efiiciency than the prior known pickling baths and having the advantage of .causing a greater flow of ferric, ferrous, and other ions from the work and consequently in a higher combined chemical and electrical efficiency;

Another object of the invention is the pro- .vision of an electric pickling system which utilizes low current densities to facilitate the removal of oxides including magnetic oxides. By-

the circuit is complete at all times, including permanent electrodes in the cell, theword complete as here used having reference to the presence at all times ofall necessary parts of the circuit for functioning, whether the circuit be open or closed, the placing of the work in the bath merely bringing it-in physical and electrical contact with a permanent electrode already present in the bath, there being no necessity for using the work itself as either electrode and there being, therefore, no necessity for clamping or otherwise attaching or securing the work in the electric circuit; and to provide such a system 1 in which the work,in large quantities if preferred, may be placed in a suitable metal basket or container, which is then merely placed in the bath to rest upon an electrode provided to receive it, the container and all the individual pieces of work therein being thus included in the electric circuit by the mere act of depositing the work in the bath.

Another object of my invention is the arrange ment of the previously mentioned permanent electrodes in the pickling tank or vat and relatively to each other so that completeand uniform ionization of the bath results. The bath being ionized uniformly throughout, therefore, acts with the same degree ,of efiiciency upon all articles placed therein regardless of their position so that the pickling and cleaning action of the bath is uniform on all articles.

It is another object of my invention to provide a pickling system wherein the work while being subjected to the action of the pickling medium is positioned in a strong magnetic field in order to increase the rate of action and,the general efiiciency of the pickling vat.

Further objects are the provision of a novel pickling system accomplishing the foregoing ob- '30 jects and advantages at low cost in actual commercial pickling practice; and to provide a system in which additional or external heating apparatus or heating energy, such as steam, are frequently not required. For example, in many cases the operation may be started with the' bath at room temperature the temperature of the bath rising as the pickling process continues, ultimately reaching an efficient' operating maximum without the use of any steam or other heating energy, 40 though it will be understood, of course, that, if desired, heat may be initially added to the bath so that it will operate at a raised temperature from the outset.

Still further objects and advantages of the invention will appear fromthe following description, in which reference is made to the accompanying'drawing, which illustrates, by way of example, one preferred form of apparatus embodying the mechanical features of the invention and in which the process of the present invention may be efficiently carried out.

In the drawing:

Fig. 1 is a plan view of a pickling tank embodying constructional features of the invention;

a Fig. 2 is a transverse sectional view of the tank of Fig. 1 taken on a plane substantially indicated by the line 2-2; and

Fig. 3 is a schematic wiring diagram of the circuit including the coil which is employed to set up the strong magnetic field within which the work to be pickled is positioned.

Composition of the bath Referring to the composition-of pickling baths prepared in accordance with the invention, the amount of water used depends, of course, on the size of the tank, and in commercial installations may vary, for example, from 100 gallons to 5,000

Percent by weight of water Heavy acids 0.50 to 25.00 Gluconic acid 0.25 to 25.00 Wetting 0.01 to 1.00

A further and more particular formula for pickling bath made up in accordance with the present invention is as follows:-

Parts by weight Water I 100 Sulphuric acid 3 to 10 d-Gluconic acid 6 to 10 A somewhat narrower range of percentages for the. addition agents is as follows:-

Percent by weight of Water Heavy acids 6.00 to 8.00 Gluconic acids 0.10 to 3.00 Wetting agent 0.05 to 0.10

A further and more specific formula for pickling bath madeup in accordance with my invention is as follows:

Parts by weight Water 100.0 Heavy acid -i 8.0 Gluconic acid 0.8 Wetting agent 0.1

Specific examples of the heavy or mineral acids given in the foregoing tables and referred to in the claims as strong acids are sulphuric acid, hydrochloric acid, nitric acid, etc.

While in the foregoing tables it has been indicated that the heavy acids may be used up to 25% by weight .of water, it should be noted that if hydrochloric or muriatic acid is used in the bath as the heavy acid, it may be used in amounts up to 50% by weight of water. The sulphuric acid used may be, for example, 66 Be. commercial sulphuric acid. The gluconic acid used in the bath in accordance with the present invention has a plurality of functions among which the following are the most important, viz:It functions as a means to disassociate the iron salts of the strong acids formed in the bath. Such disassociation has two principal advantages. Disassociation of certain of the-salts of the strong acids results in a regeneration of the strong acid.

Most of the iron-salts of the strong acid, particu-- larly iron sulphate, are so detrimental to the 0 pickling bath that when they accumulate to any appreciable extent the bath must be entirely renewed.

The second function of the gluconic acid is its effect as a primary pickling agent by directly attacking the oxide coated surface of the article being pickled. Gluconic acids are of the group of acids having a greater affinity than the mineral or heavy acids for the sub-oxides of iron which lie next to the pure metallic surface of the article to be cleaned.

In general, my invention may be distinguished over the prior art by the employment in a pickling bath of an addition agent capable of producing the above outlined desirable results. Gluconic acid is particularly suited for this purpose for the reason that it has the additional desirable characteristic as above pointed out of having a greater affinity for the sub-oxides of iron than the strong acids. The heavy or mineral acid and the gluconic acid used in the bath made up in accordance with my invention, in addition to their function as primary pickling agents, respectively have the following principal auxiliary functions, viz:The gluconic acid speeds up the primary pickling action of thestrong acid and serves as a means to disassociate the iron salts of the strong acid, i. e., freeze the acid anion of such salt; and the heavy or mineral acid renders the bath electrically conductive so that it may be readily ionized 'by the passage of an electric current, specifically an alternating current, therethrough.

It has been found that the use in a strong acid pickling bath of gluconic acid very materially reduces the time required to remove the oxide film on the article and also materially increases the life of the solution in the pickling vat, i. e., it may be used for a much longer time before it must be entirely renewed. The decrease in the pickling time is doubtless due to the accelerating effect which the gluconic acid has upon the action of the strong acid.

The gluconic acids contemplated for use in making up a pickling bath in accordance with my invention may be generally defined as an acid formed by an oxidation of at least one of the sugars of the following class, viz:-dextrose, maltose, sucrose, fructose, xylose, and decomposition products of the same. These acids may be conveniently formed or produced by a direct oxidation of the sugars, such as by adding a suitable oxidizing agent such as chlorine, bromine, iodine, etc. to glucose, along with a catalyst such as a metallic salt, particularly of the iron family. The gluconic acids may likewise be produced by fermentation process wherein to the sugar in aqueous solution is added an enzyme or fungus and permitted to ferment to produce the acid. This particular process, as w-Ell as the direct oxidation process of producing the acid is believed to be well known so that it will not require further explanation at this point.

It is important to note thatthe gluconic acids contemplated for use in accordance with my in vention may be made from materials which are not initially sugar. In other Words, it may be possible to produce these acids by beginning with a starch which is first hydrolized to produce dextrose, which is then oxidized to produce the gluconic acid. Furthermore, it may be possible to begin with a material such as cellulose which is first digested with an acid in order to convert the same to a starch which is then hydrolized to produce dextrose and then oxidized to produce the gluconic acid.

It should be noted that the term gluconic acid as used in the specification and claims should be interpreted as not limited to any specific single acid, since the material such as the sugar which is fermented or oxidized may be of such complex 'nature that several distinct acids all generally definable as gluconic acids will be produced.

Throughout the ensuing'descriptiomas well as in the appended claims, the acids of the type under discussion are referred to as those pro-- duced by an oxidation of certain named sugars. The term oxidation is herein defined as including any process for the conversion of any of the named sugars into gluconic acid derivatives and is not to be limited to an acid produced by any particular process:

The d-gluconic acid used is preferably that obtained by oxidizing commercial dextrose. The d-gluconic acid as used in the above formula is a'50% solution. The term d-gluconic acidfiin' the claims is meant to cover d-gluconic acid whether solely or as the d-gluconic acid in (d-1)- gluconic acid.

Specific examples of the wetting agents mentioned in the foregoing tables are alky-naphthalene sulphonic acid types of material, a sulphonated naphthalene derivative-commercially sold under the name-Alkanol-B powdered licorice, lignon and saponin. Specifically, the licorice may be used in amounts varying from of 1% to 1% by weight of total acid used.

It is obvious, of course, that any wetting agent used in the bath made up in accordance with my invention shall be of such nature as to 'be compatible with the materials used in the bath. The above mentioned are specific examples of wetting .agents that are thus compatible with a bath including gluconic acid and a strong acid.

Generally, the sulphonated naphthalene derivatives used as wetting agents may be present in the bath in the amounts givemin the foregoing 'of the bath, thus preventing, the trapping on such surface of explosive mixtures such asmay include hydrogen liberated from the bath.

The bath given in the foregoing example may be used in the present pickling process at a tem-- perature varying from 110 F. to 180 F., and

has been found suitable for pickling high and low carbon steel wire,=-such as nickel-chromium alloy wire annealed and normalized, the current being 60 cycle A. 0., current density varying from lampere per square foot of work surface to I amperes per square foot of work surface.

Pickling baths prepared as above have also demonstrated greatly increased efiiciency in the pickling of low carbon enamellers steel, the temperature range being from 90 F. to 160 F. and the current density varying from, 0.25 amperes to 10 amperesper square foot of work surface.

As previously indicated, the electrolytic pickling system-comprising my invention is characterized by the fact that the bath is ionized by the'passage therethrough of electric current between spaced electrodes which are permanently stationed in the bath, i. e., it is not necessary to carefully rack the work so that it may serve as 5 one of the primary electrodes. Therefore, the proper degree of ionization of the bath may be, it is believed, perhaps more accurately stated as that resulting from a particular amount of current flow per gallon of solution rather than stating the amount of current fiow in terms of the surface area of the work suspended in the bath. I have found that for various types'of work various degrees of concentration of the bath, various temperatures and other variables encountered, the amount of current fiow in the bath, in order to properly ionize the same for eflicient pickling action, may vary from one-half to 25 amperes per ,gallon of electrolyte used.

The above described use of alternating current in the bath in carrying out the principles of my invention is for the primary purpose of accelerating the chemicalreactions of the bath by causing the strong acid ions to move toward the work during the'period during which thework is anodic and organic acid ions to move toward the work during the period during which the work is cathodic, i. e., the alternating current increases the selective attack upon the oxide film of the components of the strong and organic acids.

I have discovered that the pickling action of the bath maybe materially increased byestablishing and maintaining a strong magnetic field 'so that the work being pickled and positioned in the bath occupies a position in such strong magnetic field. This acceleration of the pickling action of the bath, when the work therein is arranged in a strong magnetic field may be due to several different reas0ns:First, the strong magnetic field, if produced by an alternating current, is believed to set up eddy currents in the work causing the same to be heated, thus increasing the rateof chemical attack; second, the

molecular re-ar'rangement in the work metal due to a reversal in its magnetism may disturb the bond between the work and the adhering oxides. It may be of importance in this connection that the oxides immediately contiguous to the surface of the work are non-magnetic; whereas, those on the outer layer are magnetic.

The magnetic field above referred to may be secured-in the manner hereinafter more fully explained in connection with a description of the apparatus. It should. be noted at this point,

however, that it is believed that the frequency of the current employedin generating the magnetic field has a definite influence on the effect of such field in accelerating the pickling action of the bath.

Apparatus In the accompanying drawing, Fig. 1 illustrates a pickling tank such as may be used in carrying on the process above described comprising my invention. Such tank is substantially rectangular in form and comprises an outersupporting structure 1 which may be of wood and an inner lining.

I brought up to or maintained at a proper working temperature.

Positioned within the tank are two sets of electrodes respectively indicated by 5 and 6. The electrodes 5 connected to the bus bars '7 extend into the tank at the left end thereof as viewed in Fig. 1, and those along the bottom of the tank, as indicated at 8 in Fig. 2. The bottom sections 8 of the electrodes 5 are supported on the bottom of the tank by a plurality of cross beams 9 which have their lower faces recessed so as to prevent the collection thereunder of slime and the like.

The electrodes 6 extending into the tank from opposite sides thereof are connected to-bus bars 10 and at their lower ends are supported and maintained in proper position by means of longitudinally extending members 11. It is to be noted that the size and shape of the electrodes and their associated supporting means may vary from A that illustrated in the drawing and furthermore,

such electrodes and supporting means may be made of any suitable material which is not subject to excessive deterioration when subjected tothe action of the bath in the tank.

Attention is directed to the fact that when the electrodes 5 and 6 are arranged in the manner indicated there will be a substantially uniform current distribution throughout the electrolyte so that there will be substantially uniform ionization thereof which will result in a uniform attack by such electrolyte upon work parts which may be variously positioned within the tank.

As previously indicated, it is a feature of my invention to provide a strong magnetic field within which the work to be pickled is positioned while being subjected tothe action of the electrolyte. Such strong magnetic field may be produced by a winding such as 12 around the body of the tank. The leads from such winding are indicated at 13 and 14 in Fig. 1.

The winding, generally indicated at 12, may be energized by some suitable arrangement such as is illustrated in Fig. 3 wherein the winding 12 is in series with a secondary winding 14 of a transformer generally indicated at 15. The primary winding 16 of such transformer may be connected across any suitable power line and will have a variable resistance 17 in series therewith whereby the degree of energization of the winding 12 may' .be accurately controlled.

Large quantities of work may be pickled in accordance with the present invention, for example, quantities as large as are at present ordinarily pickled at one time in the usual sulphuric acid pickling baths, without any electric current. The work articles to be pickled may be supported in a .suitable basket of convenient size to fit the tank efficiently, such basket resting upon the hor- 'izontally extending portions 8 of the electrodes 5. The bus bars '7 and 10 are connected in an A. C. circuit in the obvious manner, the commonly used 60 cycle current being entirely suitable to carry on the invention.

' It will be understood that many variations may be made in the size and shape of the electrodes without departing from the invention; and it will also be notedthat the invention provides an electric pickling system in which only very low current densities are required, so that, although providing for the pickling of large quantities of work, the expense for current is relatively small and well overbalanced by very considerable saving in time as well as saving of heating expense and increased pickling efficiency due, not only to the fact that the electrolyte itself is of greater chemical eificiency than heretofore known pickling baths, but also to the fact that the ionization of the electrolyte results in an-increased flow of ferric and ferrous ions from the work, so that the system is one having greater combined chemical and electrical eificiency.

It will be noted that the work to be pickled may be simply deposited in the bath upon the electrodes, thus becoming a party of the alternating current circuit through the basket or baskets, when such are used, and without requiring any external or internal racking, clamping or connecting of individual pieces of work in the circuit.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I therefore particularly. point out and distinctly claim as my invention:-

1. The process of pickling a ferrous metallic article which comprises subjecting the same to the action of an acid bath which reacts with such article to form an iron salt of a strong acid, and which bath also includes a component v which will react with such iron salt to free the acid anion and form a soluble iron salt.

-2. The process of pickling a ferrous metallic article which comprises subjecting the same to the action of an acid bath which reacts with such article to form an iron salt of a strong acid, and which bath also includes a component which will react with such iron salt to free the acid anion and form a soluble iron salt, and at the same time subjecting such bath to the catalytic effect of an alternating current.

3. The process of pickling a ferrous metallic article which comprises subjecting the same to the action of an acid bath which reacts with such article to form an iron salt of a strong acid, and which bath also includes a component which will react with such iron salt to free the acid anion and form a soluble iron salt, and at the same time maintaining a strong alternating magnetic field in which said article is positioned while being thus treated.

4. The process of pickling a ferrous metallic article which comprises subjecting the same to the action of an acid bath which contains an acid selected from the group consisting of hydrochloric acid, nitric acid and sulphuric acid and an organic converting acid, which bath reacts with such article to form an iron compound which is a reaction product of an iron 'salt of the organic acid and an iron salt of the pickling acid.

5. The process of pickling a ferrous metallic article which comprises subjecting the same to.

chloric acid, nitric acid and sulphuric acid and an organic converting acid, which bath reacts with such article to form an iron compound which is a reaction product of an iron salt of the organic acid and an iron salt of the pickling acid, and at the same time subjecting such bath to the catalytic effect of an alternating current.

6. The process of. pickling a ferrous metallic article which comprises subjecting the same to the action of an acid bath which contains an acid selected from the group consisting of hydrochloric acid, nitric acid and sulphuric acid and an organic converting acid, which bath reacts with such article to form an iron compound which is a reaction product of an iron salt of 'the organic acid and an iron salt of the pickling 'altemating magnetic field in which said article being treated is positioned.

7. The processof picking a ferrous metallic article which comprises subjecting the same to the action of an acid bath which contains an acid selected from the group consisting of hydrochloric acid, nitric acid and sulphuric acid, and gluconic acid, which Jbath reacts with such article to form an iron compound which is a reaction product of an ironvsalt of the gluconic acid and an iron salt of the pickling acid.

8. The process of pickling a ferrous metallic articlewhich comprises subjecting the same to the action of an acid bath which contains an acid selected from the group consisting of hydrochloric acid, nitric acid and sulphuric acid, and.

gluconic acid, and subjectingsuch bath to the v catalytic efiect of an alternating current. V

11. Theprocess of-pickling a metallicarticle which comprises subjecting the same to the action of a bath including a strong pickling and a gluconic acid, subjecting such bathto the catalytic effect of an alternating current and establishing a strong alternating magnetic field within which said article to be pickled is positioned;

12. The process of pickling which comprises subjecting the article to be pickled to the action of a bath including'a strong pickling acid, "a gluconic acid and a'wetting agent compatible with said bath;

' 13. The process of pickling which comprises subjecting the article to be pickled to the action ofa bath including a strong pickling acid, a

. gluconic acid and a wetting agent compatible with i said bath; and subjecting such bath to the catalytic action of an alternating current.

g a ferrous article.

subjecting a ferrous article to be pickled to the actionof a bath including sulphuric acid and a gluconic acid.

v15. The process of pickling which comprises subjecting a. ferrous article to be pickled to the action of a bath including sulphuric acid and a gluconic acid, and subjecting such bath to the 7 and a gluconic acid.

1'7. The process of pickling which comprises subjecting a ferrousarticle to be.pickled to the action of a bath including hydrochloric acid, a gluconic acid and a wetting agent, compatible with such bath, and ionizing such bath.

18. The process of pickling which comprises subjecting a ferrous article to be pickled to the action of a bath including nitric acid and a gluconic acid.

19 The process of pickling which comprises subjecting a ferrous article to be pickled to the action of a bath including nitric acid, a gluconic acid and a wetting agent, and subjecting .such bath to the catalytic efiect .of an alternating current.

20. A pickling bath containing a gluconic acid in amounts from about 0.25% to about 50%..

21. A pickling bath. containing a substantial quantity of gluconic acid and a wetting agent compatible with said bath.

22. A pickling bath. containing a strong pick ling acid and a gluconic acid;

23. A pickling bath containing an aqueous sul' phuric acid solution and gluconic acid.

" 2-1. A pickling bath containing an aqueous hy- 26. A pickling bath containing a substantial" quantity of d-gluconic acid.

27. A pickling bathcontaining from about 0.50% to about 25.00% of an inorganic acid selected from the group consisting of hydrochloric acid, nitric acid and sulphuric acid, from about 0.25% to about 50.00% of gluconic acid and from 0.01% to about 1.00% of a wetting agent compatible with said bath, and the remainder being substantially water.

. ALLAN n. CHESTER. 

